I wanted to go for something creepy, but I liked the idea of an item that appears threatening without actually causing harm. Something about that struck me as almost more frightening in a way, because it's unclear what the SPC might actually be doing to people.

I think you might want to make sure that it says "SCP" and not "SPC" in every instance (since this appears to be a Special Containment Procedures document and not a Selachian Pugnatorial Capabilities project…)

The problem is that it never goes past that core idea, which is one of the big differences between an anomalous object and an SCP. SCP's are unusual by the standards of a group that has formalized classification systems for types of ghosts and ways something can end the world. (Thus they have Special Containment Procedures as opposed to the typical containment procedures.)

A tape that just induced fear would be an anomalous object. The part about it only working once per person, and changing languages are interesting, but that still makes it more like a particularly advanced version of things they see every week. What makes this one get flagged as an SCP rather than sent to the warehouse as Anomalous Object # 20R6T95? Is there something deeper going on here (say, was this trial one of some larger project?) What's the significance of Dec 1972 and the initials LC? Is there something unique about how it works that differs from standard memetic fear inducers?

So long story short, what you have here is a fairly stock item, but with some little hints of something that I think I kind of like in spite of that. I'd suggest embracing that, and thinking of this as something so run-of-the-mill and harmless that they almost missed something very important or unusual about it.